Mixed-flow fan and method of making



. Sept. 8, 1964 c. A. HATHAWAY MIXED-FLOW FAN AND METHOD OF MAKING 3 Sheets-Sheet 1 Filed NOV. 16, 1959 INVENTOR HARL ES A. HA THAWA r A TTORNEYS P 8, 1964 c. A. HATHAWAY v 3,147,541

MIXED-FLOW FAN AND METHOD OF MAKING Filed Nov. 16, 1959 v 3 Sheets-Sheet 2 FIG.16

TOR

INVEN CHARLES AHATHAWAV Sept. 8, 1964,

Filed Nov. 16, 1959 FIG. 7 I! c. A. HATHAWAY 3,147,541

MIXED-FLOW FAN AND us'mon OF MAKING 3 Sheets-Sheet 3 INVENTOR CHARLES .4. HATHA WAY Milk ATTORNEYS United States Patent MIXED-FLOW FAN AND METHOD OF MAKING Charles A. Hathaway, Litchfield, Conn., assignor to The Torrington Manufacturing Company, Torrington, Conn., a corporation of Connecticut Filed Nov. 16, 1959, Ser. No. 853,250 3 Claims. (Cl. 29-1563) The invention relates to air moving fans of the mixedflow type, fans of this type having performance characteristics between those of axial-flow fans and those of centrifugal fans.

One object of the invention is to provide a fan of the stated type having improved means for rigidly connecting the several fan parts with each other.

Another object of the invention is to provide, in association with a fan of the stated type, an auxiliary rotatable ring having advantageous characteristics.

Other objects of the invention are to provide suitable separate fan parts which are particularly adapted for use in the making of fans of the stated type.

Another object of the inventionis to provide an effective and low cost method for making fans of the stated type.

Other objects of the invention will be apparent from the drawings and from the following specification and claims. a

The drawings show a preferred embodiment of mechanical features of the invention and they illustrate the presently preferred method steps of the invention. Said embodiment and said method steps will be described, but it will be understood that various changes may be made from the construction and the method disclosed, and that the drawings and description are not to be construed as defining or limiting the scope of the invention, the claims forming a part of this specification being relied upon for that purpose.

. Of the drawings:

FIG. 1 is a front view of a fan embodying the invention with the upper portion of the shroud broken away to more clearly show the blades.

FIG. 2 is a combined side and vertical section view of the fan, the sectional portion of the view being taken along the line 2-2 of FIG. 1.

FIG. 3 is a developed fragmentary sectional view taken along the line 3-3 of FIG. 2.

I FIG. 4 is a fragmentary sectional view taken along the line 4-4 of FIG. 2.

FIG. 5 is a fragmentary side view generally similar to FIG. 1, but showing-an alternative embodiment of the invention.

FIG. 6 is a fragmentary sectional view generally similar to FIG. 2, but showing the same embodiment as FIG. 5. I

FIG. 7 is an enlarged fragmentary view of the intake shroud, this view being taken in the direction of the arrow at the left in FIG. 11.

FIG. 8 is a fragmentary sectional view taken along the line 8-8 of FIG. 7.

FIG. 9 is a fragmentary edge view of one blade.

. FIG. 10 is a fragmentary plan view of the backplate with the backplate in the position shown in FIG. 12.

FIG. 11 is a fragmentary sectional view taken along the line 11-11 of FIG. 10.

FIG. 12 is a schematic central vertical sectional view illustrating one assembly step included in the method of the invention.

FIG. 13 is a view generally similar to FIG. 11, but illustrating another assembly step included in the method of the invention.

FIG. 14 is an enlarged fragmentary sectional view of a metal sheet such as may be used for some of the fan parts.

FIG. 15 is an enlarged fragmentary sectional view taken along the line 15-15 of FIG. 4.

FIG. 16 is an enlarged fragmentary sectional view taken along the line 16-16 of FIG. 4.

FIG. 17 is an enlarged fragmentary sectional view taken along the line 17-17 of FIG. 1.

General Description As has been stated, a fan embodying the invention is of the mixed-flow type. It is rotatable about a central axis and is adapted to receive air moving in a rearward axial direction and to discharge the air outwardly in approximately radial directions. As shown in FIGS. 1 to 4 of the drawings, the fan comprises an annular backplate 10 rigidly secured to a central hub 12, a plurality of blades 14, 14 equally spaced circumaxially and connected at their corresponding rear edges 16, 16 with said backplate 10, and an annular inlet or intake shroud 18 to which said blades 14, 14 are connected at their opposite front edges 20, 20. The blades have inner intake edges 22, 22 and they have outer discharge edges 24, 24. Each blade 14 is so shaped that it is concave at its leading face and is convex at its trailing face. The number of blades can be varied, but for the minimum of noise the number of blades is preferably a prime number. As shown, there are nineteen blades. Preferably and as shown, the backplate 10 has a folded peripheral edge portion 26 and the shroud 18 has a folded peripheral edge portion 28. c The hub 12 may be connected to the shaft 30 of a motor 32 shown in FIG. 2. The backplate 10 is deepdished or coned and this not only provides approximate conformity with the path of air flow, but also provides space for receiving a portion of said motor 32.

a The backplate 1t and the shroud 18 provide an annular passageway for the air which enters in the axial direction at the front as shown by the arrows R, R in FIG. 2,

and is discharged generally radially as indicated by the arrows S, S. The backplate and the shroud are preferably curved in axial section so as to generally conform to the curved path of air flow. The backplate has'a main annular portion which is forwardly concave and the shroud has a main annular portion which is rearwardly convex.

The blades 14, 14 extend between the backplate and the shroud and theyare shaped at their rear'and front edges 16 and 20 to conform to the contours of the forwardly concave main portion of the backplate and the rearwardly convex main portion of the shroud. The leading inner edges 22, 22 of the blades are inclined inwardly and rearwardly throughout their entire lengths as shown in FIG.

2. When the blades are positioned as shown, the fan is rotatable in the clockwise direction as indicated by the several arrows in FIGS. 1, 3 and 4.

As before stated, the backplate 10 is rigidly secured to the hub 12. Preferably and as shown, a disc 34 is also secured to the hub, this disc serving to reinforce the inner portion of the backplate. The hub 12 initially has a re 3 duced diameter at its right end as viewed in FIG. 2. The backplate and the disc 34 are centrally apertured so as to fit the smaller end portion of the hub. During assembly, the hub is entered in the apertures in the backplate and disc, and then the right end portion of the hub is spun or peened to engage and retain said backplate and disc. The disc 34 is suitably connected with the backplate 10, rivets 36 being shown for this purpose.

Air Guiding Ring As shown in FIGS. 5 and 6, the fan may be provided with an imperforate auxiliary ring at the intake side thereof. This ring may be varied as to size and shape, but as shown there is a ring 38 which comprises a portion 40 curved in cross section and riveted or otherwise connected to the shroud 18 at the intake end thereof. The ring 38 further comprises an annular flat portion 42 extending from the curved portion 40 and having a diameter somewhat greater than the diameters of the backplate and the shroud. The portion 42 of the ring may have radial reinforcing ribs 43.

When a ring such as 38 is provided, the fan may advantageously be located at an aperture 44 in a partition 46. The aperture 44 has a diameter slightly greater than the maximum diameter of the fan proper so that the fan may be inserted through the aperture, toward the right as viewed in FIG. 5. The flat portion 42 of the ring 38 is close to the partition and the diameter of the aperture 44 is somewhat less than the diameter of the ring so as to provide a limited sealing effect which prevents any substantial air movement through the aperture and around the fan. The ring 38 serves as a means for guiding air into the intake end of the fan.

Preferably, the ring 38 is adapted to also serve as a slinger ring and it has a cylindrical flange 48 carried by the fiat portion 42 and extending in the forward direction.

Means for Connecting Blades With Shroud and Steps in Assembly Method As shown in FIGS. 7, 8 and 12, the shroud 18 is provided with a plurality of circumferentially spaced rows of slots 50, 52, the number of rows of slots being the same as the number of blades 14, 14. Each blade 14 at the front edge thereof has a plurality of tapered integral tabs 54, 56, the number of tabs on each blade being the same as the number of slots in each row. As shown, there are two tabs on each blade and two slots in each row, the rows being inclined in accordance with the required inclination of the blades. The tabs 54, 56 and the slots 50, 52 conform with each other as to size and spacing. The tabs extend through and at least approximately fit the slots, and the end portions of the tabs are bent over so as to be immediately adjacent the front face of the shroud. By means of the bent tabs, the blades and the shroud are held in locked engagement.

The dimensions of the tabs and slots may be such that each tab tightly engages its slot when assembly is completed. When tight engagement is necessary, each of said slots 50, 52 has at least one dimension that is initially slightly less than the corresponding dimension of the immediately adjacent corresponding tab 54 or 56. As the result of the foregoing, the tab can be fully entered in the slot only by the application of pressure. When pressure is applied to effect complete assembly there is interdeformation between the tab and the walls of the slot, one or the other or both of said parts being deformed. Otherwise stated, there is a crushing engagement between said tab and said slot walls. The result is that there is a very firm gripping of each tab within its slot. As specifically illustrated, the length a of each slot 50, 52 at the ends thereof is slightly less than the length b of the corresponding tab. Alternatively, the width 0 of each slot 50, 52 at the ends thereof may be slightly less than the thickness d of said tab. The slot dimensions are shown in FIG. 7 and the blade dimensions are shown in FIG. 9. As presently preferred, each slot has a straight side and 4 has two straight ends perpendicular to said straight side and has a concave side opposite said straight side.

The shroud 18 at any radial plane therethrough is inclined outwardly from the axis of rotation and away from a reference plane perpendicular to said axis. The reference plane may be the plane at the front of the shroud as shown in FIG. 2. The shroud is convex in directions which are inclined toward said axis and away from said plane, one of these directions being indicated by the arrow in FIG. 12. The last said direction is approximately perpendicular to the direction of inclination. To facilitate assembly, the walls of all of the shroud slots in each row, that is, the walls of each two slots 50 and 52, are parallel with each other and they extend in the last said direction.

The tabs 54, 56 on each blade 14 have their center lines parallel with each other and said center lines are inclined so as to be parallel with the walls of the slots when the blade is positioned for assembly as shown in FIG. 12.

When the slots and tabs are shaped and positioned as shown, the tabs on each blade can be simultaneously entered in the corresponding slots in the shroud when the blade is moved toward the shroud and in said inclined direction. The tabs are tapered and the wider central portions of the slots facilitate the initial entry of the tabs in the slots. After initial entry of the tabs, the blade is moved into its fixed position and then the projecting end portions of the inserted tabs are bent to lock the blade to the shroud. When the slot and tab dimensions are such as the require interdeformation, considerable pressure must be applied to engage each blade with the shroud.

Certain features of the described tabs and slots are not claimed herein, but they are set forth and claimed in the copending application of Charles A. Hathaway, Serial No. 666,847, filed June 20, 1957, and entitled Centrifugal Blower Wheel and method of making, now Patent No. 2,932,445, dated April 12, 1960.

Means for Connecting Backplate With Blades and Steps in Assembly Method As shown in FIGS. 10, 11 and 13, the backplate 10 is provided with a plurality of circumferentially spaced rows of slots 58, 60, 62, the number of rows of slots being the same as the number of blades 14, 14. Each blade 14 at the rear edge 16 thereof has a plurality of tapered integral tabs 64, 66, 68, the number of tabs on each blade being the same as the number of slots in each row. As shown, there are three tabs on each blade and three slots in each row, the rows being inclined and curved in accordance with the required inclination and curvature of the blades. The tabs 64, 66, 68 and the slots 58, 60, 62 conform with each other as to size and spacing. The tabs extend through and tightly fit the slots and the end portions of the tabs are bent over so as to be immediately adjacent the rear face of the backplate. By means of the bent tabs, the blades and the backplate are held in locked engagement.

As to the last said details, the slots and tabs may be the same as those previously described in connection with the shroud. Repetition of the description is unnecessary.

It has been stated that the tabs 54, 56 on each blade are inclined for entry into the slots 50, 52 in the shroud, this being shown in FIG. 12. When the tabs 54, 56 are so inclined, the tabs 64, 66, 68 on the blades have their center lines parallel to the central axis and at an angle to the center lines of the tabs 54, 56. All of the slots 58, 60, 62 in the backplate have their walls parallel with each other and parallel with the central axis. To facilitate assembly the tabs 64, 66, 68 in each row have different lengths. As shown, the inner tab 64 in each row is the longest and the outer tab 68 in each row is the shortest.

After the blades have been connected with the shroud,

as previously described and as shown in FIG. 13, the backplate is moved in the axial direction and toward the blades, the movement being downward as shown in said FIG. 13. Inasmuch as the center lines of the tabs 64, 66, 68 and the walls of the slots 58, 60, 62 are all parallel with the central axis, the tabs can freely enter the slots.

Assembly is facilitated by the provision of longer tabs such as 68, 68 in the several rows. If the tabs were all of the same length and if there were nineteen blades, there would be fifty-seven tabs to be simultaneously entered. But with the provision of said longer tabs such as 68, 68, there are only nineteen tabs to be simultaneously entered. When said longer tabs have been entered they serve as pilots for the entry of the shorter tabs. As previously explained, tab entry is facilitated by the provision of slots with wider central portions.

After initial entry of the tabs, the backplate is pressed into its fixed position and then the projecting end portions of the inserted tabs are bent to lock the backplate to the blades.

Filler Metal at Crevices and Step in Assembly Method FIG. 14 is an enlarged sectional view of a metallic sheet 70 such as may be used for some or all of the sheet metal parts of the fan. The sheet 70 comprises a parent sheet 72 formed of a metal such as aluminum, and further comprises coatings 74, 74 at opposite sides of the sheet 72. The coatings are formed from a metal such as a brazing alloy that is fusible at a temperature much lower than the melting temperature of the parent metal.

Coated sheets may be used for making all of the blades and for making the shroud and the backplate. Ordinarily, however, it is sufiicient to use the coated metal only for the blades or only for the shroud and backplate. The blades can be regarded as constituting one group of parts and the shroud and backplate can be regarded as constituting another group of parts.

When the coated metal has been used for making the parts of at least one of said groups, the entire fan, after assembly, is heated in a liquid bath or otherwise to a temperature above the melting or fusing temperature of the filler metal and below the melting temperature of the parent metal. The molten filler metal flows by capillary action into all re-entrant angles between the fan parts and into all crevices between the edges of the blades and the shroud and backplate and into all crevices within said slots in the shroud and backplate and into all crevices between the end portions of said tabs and the respectively adjacent faces of the shroud and backplate. Any surplus filler metal that does not adhere by capillary action falls away and the parent metal remains without any coating thereon.

From the foregoing description of the final step of the method, it will be apparent that in the completed fan there are fillers 76 in all crevices between the edges of the blades and the shroud and backplate as shown in FIG. 16. It will also be apparent that there are fillers '78 in all crevices within said slots in the shroud and backplate and fillers 80 in all crevices between the end portions of said tabs and the respectively adjacent faces of the shroud and backplate as shown in FIG. 15. It will further be apparent that there are fillets 82 at all reentrant angles between the fan parts. There are also fillers 84 in any spaces between the backplate and the reinforcing disc 34 as shown in FIG. 17.

A fan having the described fillers and fillets has several advantages, some of which are as follows. The several fillers and fillets provide reinforcement at the connections of the blades with the shroud and backplate thus making it possible to use thinner metal than would otherwise be necessary. There is a substantial reduction in the noise caused by the fan during operation, this reduction resulting partly from the elimination of any rattle and partly from the elimination of any air flow through various 6 narrow crevices. Less accuracy isrequired in the initial formation of the tabs on the blades and of the slots in the shroud and in the backplate, this being due to the fact that all crevices are in any event filled.

The invention claimed is:

1. An arcuate sheet metal blade blank for use in making a mixed-flow fan, said blade blank having opposite edges adapted respectively to constitute the outer and inner edges of a blade of the fan and having other oppo site edges respectively concave and convex and adapted respectively to engage and fit a convex shroud and a concave backplate of the fan, said blade blank having in tegral tapered tabs that extend from said concave edge thereof and are adapted to extend through slots in the shroud which tabs have their center lines parallel with each other, and said blade blank having integral tapered tabs that extend from said convex edge and are adapted to extend through slots in the backplate which last said tabs have their center lines parallel with each other and with the axis of the backplate and at an angle to the center lines of the first said tabs.

2. A sheet metal blade blank as set forth in claim 1, wherein there are at least three tabs at said convex edge and wherein the last said tabs have different lengths measured from said convex edge.

3. A method for making a mixed-flow fan comprising the steps of: providing first and second groups of sheet metal parts wherein the parts of at least one group are formed from composite sheets each comprising a parent metal and coatings thereon of a readily fusible filler material, providing from the parts of one of said groups of parts a shallow convex annular intake shroud with a plurality of circumaxially spaced rows of slots therein, providing from the parts of the other of said groups of parts a plurality of blade blanks each having opposite concave and convex edges each of which edges is provided with rows of tabs, the tabs on the concave edge of each blade conforming in size and spacing to the slots of one row in the shroud and the tabs on the convex edge of each blade having center lines which extend parallel to the shroud axis, positioning the several blade blanks adjacent the shroud and inserting the tabs at said concave edges into the corresponding shroud slots, bending the projecting end portions of the inserted tabs to lock the blade blanks to the shroud, providing from the parts of said one group of parts an annular backplate having a shallow outer portion with a plurality of circumaxially spaced rows of slots therein, the said slots conforming in size and spacing to the tabs at the convex edges of the assembled blade blanks, positioning the backplate with its concave portion adjacent said assembled blade blanks and effecting relative axial movement between said backplate and the assembled blade blanks and shroud to insert the tabs at the convex edges of said blanks into corresponding slots in the backplate, bending the projecting end portions of the last said inserted tabs to lock the backplate to the blade blanks, and heating the entire assembly to cause some of the filler metal to become molten and flow by capillary action so as to constitute fillets at all reentrant angles between the fan parts and so as to fill all crevices between the edges of the blades and the shroud and backplate and all crevices within said slots and between the end portions of said tabs and the respectively adjacent faces of the shroud and backplate.

References Cited in the file of this patent UNITED STATES PATENTS 963,378 Lorenz July 5, 1910 1,602,009 Germeyer Oct. 5, 1926 1,637,652 Ness Aug. 2, 1927 1,873,974 Meyer Aug. 30, 1932 1,876,518 Mathis Sept. 6, 1932 (Other references on following page) ERNEST W. SW-IDER UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No 3 l 4T 54l September 8 1964,

Charles A0 Hathaway It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Columnml. line 31 for "the". read to column 6 line 47, a-fter "shall-ow" insert concave Signed and sealed this 19th day of January 1965 (SEAL) Attest:

EDWARD J. BRENNER Attesting Officer Commissioner of Patents 

3. A METHOD FOR MAKING A MIXED-FLOW FAN COMPRISING THE STEPS OF: PROVIDING FIRST AND SECOND GROUPS OF SHEET METAL PARTS WHEREIN THE PARTS OF AT LEAST ONE GROUP ARE FORMED FROM COMPOSITE SHEETS EACH COMPRISING A PARENT METAL AND COATINGS THEREON OF A READILY FUSIBLE FILLER MATERIAL, PROVIDING FROM THE PARTS OF ONE OF SAID GROUPS OF PARTS A SHALLOW CONVEX ANNULAR INTAKE SHROUD WITH A PLURALITY OF CIRCUMAXIALLY SPACED ROWS OF SLOTS THEREIN, PROVIDING FROM THE PARTS OF THE OTHER OF SAID GROUPS OF PARTS A PLURALITY OF BLADE BLANKS EACH HAVING OPPOSITE CONCAVE AND CONVEX EDGES EACH OF WHICH EDGES IS PROVIDED WITH ROWS OF TABS, THE TABS ON THE CONCAVE EDGE OF EACH BLADE CONFORMING IN SIZE AND SPACING TO THE SLOTS OF ONE ROW IN THE SHROUD AND THE TABS ON THE CONVEX EDGE OF EACH BLADE HAVING CENTER LINES WHICH EXTEND PARALLEL TO THE SHROUD AXIS, POSITIONING THE SEVERAL BLADE BLANKS ADJACENT THE SHROUD AND INSERTING THE TABS AT SAID CONCAVE EDGES INTO THE CORRESPONDING SHROUD SLOTS, BENDING THE PROJECTING END PORTIONS OF THE INSERTED TABS TO LOCK THE BLADE BLANKS TO THE SHROUD, PROVIDING FROM THE PARTS OF SAID ONE GROUP OF PARTS AN ANNULAR BACKPLATE HAVING A SHALLOW OUTER PORTION WITH A PLURALITY OF CIRCUMAXIALLY SPACED ROWS OF SLOTS THEREIN, THE SAID SLOTS CONFORMING IN SIZE AND SPACING TO THE TABS AT THE CONVEX EDGES OF THE ASSEMBLED BLADE BLANKS, POSITIONING THE BACKPLATE WITH ITS CONCAVE PORTION ADJACENT SAID ASSEMBLED BLADE BLANKS AND EFFECTING RELATIVE AXIAL MOVEMENT BETWEEN SAID BACKPLATE AND THE ASSEMBLED BLADE BLANKS AND SHROUD TO INSERT THE TABS AT THE CONVEX EDGES OF SAID BLANKS INTO CORRESPONDING SLOTS IN THE BACKPLATE, BENDING THE PROJECTING END PORTIONS OF THE LAST SAID INSERTED TABS TO LOCK THE BACKPLATE TO THE BLADE BLANKS, AND HEATING THE ENTIRE ASSEMBLY TO CAUSE SOME OF THE FILLER METAL TO BECOME MOLTEN AND FLOW BY CAPILLARY ACTION SO AS TO CONSITUTE FILLETS AT ALL REENTRANT ANGLES BETWEEN THE FAN PARTS AND SO AS TO FILL ALL CREVICES BETWEEN THE EDGES OF THE BLADES AND THE SHROUD AND BACKPLATE AND ALL CREVICES WITHIN SAID SLOTS AND BETWEEN THE END PORTIONS OF SAID TABS AND THE RESPECTIVELY ADJACENT FACES OF THE SHROUD AND BACKPLATE. 